High energy emission from supernova remnants and regions of star formation Diego F. Torres...

High energy emission from supernova High energy emission from supernova remnants and regions of star formation remnants and regions of star formation

Diego F. TorresDiego F. [email protected]

Lawrence Livermore Lab.California, 94550, USA www.angelfire.com/id/dtorres

SummarySummary

SNRsSNRs EGRET sources and SNRSEGRET sources and SNRS GLAST/MAGIC prospectsGLAST/MAGIC prospects SNRs searched at TeV energies with HESSSNRs searched at TeV energies with HESS

Unidentified gamma-ray sources at TeVUnidentified gamma-ray sources at TeV Multiwavelength informationMultiwavelength information Possible ideas for an explanation Possible ideas for an explanation

Star forming galaxies at TeVStar forming galaxies at TeV Modeling for Arp 220 with Q-diffuseModeling for Arp 220 with Q-diffuse

: : not within this talk.not within this talk.(Torres et al. ApJ Letters 601, (Torres et al. ApJ Letters 601,

75, 2004)75, 2004)

Gamma-rays from Supernova RemantsGamma-rays from Supernova Remants

Torres et al. Physics Reports 382, 303, 2003and references therein + some new results, especially Aharonian et al.’s from HESS

Spectrum of cosmic rays

The bulk of CRs occurs with energies below the knee and are thought to come from our own galaxy.

Accelerated electrons, ok. Accelerated protons?Accelerated electrons, ok. Accelerated protons?

Cassiopeia A

Crab

Shock front

Molecular cloud

protons, electrons

Synchrotron radiation

e

p

Since CRs are deflected by the galactic magnetic field, they do not preserve the information on the location of their source. We must, consequently, look for electromagnetic signatures produced by the protons and ions during their acceleration.

Spatially coincident pairs of SNRs and unidentified EGRET sources


Identifying the pairs


Data contained in the3EG


Variability Variability indices


Variability

Some of the sources are variable. Not related to SNRsSome of the sources are variable. Not related to SNRs

3EG J0535+2610

Big variations in the measured fluxfor adjacent viewing periods.

Romero, Torres et al. A&A, 376, 599, 2001Anchordoqui, Torres, et al. ApJ, 2003 neutrino yield detectable at Earth!

High Resolution radio map of the nearby star LS 5039 obtained with VLBA and VLA in phased array mode (similar to a single dish of 115m) at 6 cm.

The presence of radio jets is the main evidence supporting its microquasar nature.

Contours shown go from 6-50 times 0.085 mJy per beam, the rms noise. The map is centered at the star position. 1 milliarcsec is equivalent to 3AU (~1013 cm) for a distance of 3kpc.

3EG J1824-1514

Paredes et al. Science 288, 2340


Known data for the SNRs

From Torres et al. 2003, Physics ReportsFrom Torres et al. 2003, Physics Reports

Most plausible cases appear to present broad correlationsMost plausible cases appear to present broad correlations

Torres et al. 2004, Adv. In Space PhysicsTorres et al. 2004, Adv. In Space Physics

The GeV futureThe GeV future

RX J2020.3+4026

(Pulsar)

W66W66

SN1006 – the prototype ?

CANGAROO 1997 – the small single telescope observations

but H.E.S.S. 2004...

Some recent results from HESSSome recent results from HESS

The panorama for SNR G347.3-0.5 (RX J1713.7-3946 ) )

ROSAT X-ray contours. Emission from the bulk of the SNR rim can be seen with particular enhancements along the west/northwest regions, where bright non-thermal radio emission is also seen. The total radio flux is well below 10 Jy, Slane et al. ApJ 525, 357 (1999)

Red depicts the TeV significance contours. The flux was (5.3 ± 0.9 [statistical] ± 1.6 [systematic]) x 10-12 photons cm-2 s-1 (at E>1.8 ± 0.9 TeV). Muraishi et al. AA354, L57 (2000).

While electrons give rise to the bulk of the non-thermal radio, X-ray and TeV emission in the NW, the CR protons and ions are exposed at GeV energies via their hadronic interactions in the dense material of

cloud A, leading to pion gamma-decay GeV emission in the NE.

1st SNR at TeV energies !SNR RX J1713.7-3946 has all the ingredients: extreme X-ray bright, EGRET source nearby, dense molecular cloud region

Butt et al. 2001

Aharonian et al. Nature October 2004Aharonian et al. Nature October 2004But...But...

evidence for hadronic particle acceleration in SNRs still unclear.

-> SNR RX J1713.7-3946

Enomoto et al. 2002 (Nature)

IC interpretation in conflict with data

Butt, Torres et al. 2002 (Nature), Reimer & Pohl 2002 (A&A)

0 interpretation in conflict with data, too !

Interpretation still in doubt...Interpretation still in doubt...

Partial SummaryPartial Summary

SNRs are TeV sources! (Even using Whipple criterion – SNRs are TeV sources! (Even using Whipple criterion – accepting observations by CANGAROO on G347.3-0.5)accepting observations by CANGAROO on G347.3-0.5)

Thus, evidence suggests that some of them should also be GeV Thus, evidence suggests that some of them should also be GeV sources, and all theoretical models for GLAST and MAGIC sources, and all theoretical models for GLAST and MAGIC energy ranges await testing.energy ranges await testing.

Proton acceleration up to TeV energies yet awaits testing.Proton acceleration up to TeV energies yet awaits testing.

Gamma-rays from Luminous and Ultra Gamma-rays from Luminous and Ultra Luminous Infrared GalaxiesLuminous Infrared Galaxies

Torres, Reimer, Domingo, Digel ApJ Letters, 607, 99-102 (2004)

Torres Arp 220ApJ, 617, 966 (2004)

Cillis, Torres & Reimer 2005ApJ in press

Gamma-ray emission from the interstellar mediumGamma-ray emission from the interstellar medium

High-energy gamma-rays are produced in cosmic-ray interactions with interstellar gas and photons Cosmic-ray production is associated with regions of massive star

formation (e.g., SNRs, colliding OB stellar winds) This represents approximately 90% of the high-energy gamma-ray

luminosity of the Milky Way (~106 solar)

~60% of all EGRET gamma-rays were diffuse emission from the Milky Way

Diffuse emission from external galaxiesDiffuse emission from external galaxies

Only one other external galaxy detected in the light of its diffuse emission – LMCOnly one other external galaxy detected in the light of its diffuse emission – LMC The problem is distance: Milky Way at 1 Mpc would have a flux of about 2.5 x The problem is distance: Milky Way at 1 Mpc would have a flux of about 2.5 x

1010-8-8 cm cm-2-2 s s-1-1 (>100 MeV), well below EGRET’s detection limit (>100 MeV), well below EGRET’s detection limit

LMC

(1.9 ± 0.4) x 10-7 cm-2 s-1

EGRET IRAS

30 Doradus: extensive massive SFR and molecular clouds

Nearby Starbursts: Upper limits with EGRET data

[Akyuz et al. 1992, Volk et al. 1996, Paglione et al. 1996, Bloom et al. 1999]

10 starbursts selected by distance (<10Mpc),Infrared luminosity (>109 Lsolar) at latitudes |b|>10.

Bloom et al. 1999

NGC 253 Average M82

Energy [MeV]

Flu

x [p

hoto

ns

cm-2 s

-1 M

eV

-1]

Left: Time-evolution of a galactic encounter, viewed along the orbital axis. Here dark halo matter is shown in red, bulge stars are yellow, disk stars in blue, and the gas in green.

Barnes and Hernquist 1996: merging of gas-rich galaxies

Right: showing only gas in both galaxies

Almost all ULIRGs seems to be double or Almost all ULIRGs seems to be double or interactinginteracting

[review on LIRGs and ULIRGs: Sanders and Mirabel, ARA&A, 1996]

Only one within the 100 Mpc sphere [Arp 220]

And there are tens of LIRGs (luminosities >1011 LSUN): detectability depends on the combined effect of distance and starburst activity.

MW

CR Enhancement required for detectability/LAT

Detectability of LIRGsDetectability of LIRGs

Gamma-ray detectability is favored in Gamma-ray detectability is favored in starburst galaxies (Akyuz, Aharonian, starburst galaxies (Akyuz, Aharonian, Volk, Fichtel, etc)Volk, Fichtel, etc) Large Large MM, with high average gas , with high average gas

density, and enhanced cosmic ray density, and enhanced cosmic ray densitydensity

Recent Recent HCN-lineHCN-line survey of Gao & survey of Gao & Solomon (2004) of IR and CO-bright Solomon (2004) of IR and CO-bright galaxies, and nearby spirals galaxies, and nearby spirals Allows estimate of SFR (from HCN Allows estimate of SFR (from HCN

luminosity) and minimum required luminosity) and minimum required kk for detection by LAT and IACTs (from for detection by LAT and IACTs (from HCN + CO intensities and distance)HCN + CO intensities and distance)

Several nearby starburst galaxies and a Several nearby starburst galaxies and a number of LIRGs and ULIRGs are number of LIRGs and ULIRGs are plausible candidates for detectionplausible candidates for detection

Arp 220Arp 220

The best studied and nearest ULIRG (72 Mpc)The best studied and nearest ULIRG (72 Mpc)

Arp 220’s center has two radio-continuum and two IR sources, separated by ~1 arcsec (e.g., Scoville et al. 1997, Downes et al. 1998, Soifer et al. 1999, Wiedner et al. 2002).

The two radio sources are extended and nonthermal (e.g., Sopp & Alexander 1991; Condon et al. 1991; Baan & Haschick 1995), and likely produced by supernovae in the most active starforming regions.

CO line, cm, mm-, and sub-mm continuum (e.g., Downes & Solomon 1998) as well as recent HCN line observations (e.g., Gao & Solomon 2004a,b) are all consistent with these two sources being sites of extreme star formation and having very high molecular densities.

Other less luminous candidates –if closer- can be detected.Other less luminous candidates –if closer- can be detected.

Downes & Solomon 1998, Gao & Solomon 2004

Arp 220

~350 pc

Arp 220: Geometry

Arp 220: Supernova explosion rates

18 cm VLBI (3 x 8 milliarcsec resolution) continuum imaging of Arp 220 has revealed the existence of more than a dozen sources with 0.2-1.2 mJy fluxes (Smith et al. 1998), mostly in the western nucleus. In November 2002, new observations with VLBI revealed 30 supernova remnants candidates, 20 in the western, and 10 in the eastern nucleus.

All, the previous result, models of the nuclei using Starburst99 (Shioya et al. 2001); and relationships between the infrared luminosity and the rate of supernova explosions (Van Buren et al. 1994, Manucci et al. 2003) suggest that the rate is ~2 yr ( ! )

This rate is ~300 times larger than the largest of the Local Group Galaxies (M31: ~0.9 SN/century)

7 hours, 17 telescopes. Size of the sources ~0.1 pcNo single compact, central core, as in AGNsHigh brightness argues for non-thermal origin

High energy emission computed from first principlesHigh energy emission computed from first principles

Q-DIFFUSE set implements

Spectral computation of secondary and tertiary particles and their emissions at different frequencies (pions, muons, electrons, positrons, neutrinos)

Solution of the diffusion-loss equation => steady population of particles

Radio emission through synchrotron and free emission of primary and secondary electrons

Free-free absorption processes IR and FIR spectra through the dust emissivity Gamma-emission through Brem, IC, of the primary and

secondary populations and pion decay (emission of the steady distributions)

Minimize the set of assumptions, relate them to observations

Q-DIFFUSSE

SN rate, mass, density, & IR luminosity

Injection proton and electron spectrum, diffusion/escape timescales

diffusion-losses: steady spectrum of protons & electrons

Secondary production: knock-on process,neutral and charged pion decay

Synchrotron, IC, Bremsstrahlung, Pion Decay. Absorption of gamma-rays, opacities, eq. of radiation transport.

Model predictions from radio to IR with emission of secondaries, FIR with emission of dust. Parameter fixing: B-field.

Model Predictions at high energy: gamma-rays, cosmic-ray & neutrino fluences. Comparison with corresponding sensitivities of RXTE, INTEGRAL, GLAST, ICECUBE, MAGIC, HESS at each energy band.

2nd and 3rd generation of particles is computed with the steady spectrum of protons. Electron and positron sources taken into account to define the steady steady electron distribution

Q-DIFFUSSEObservational measurements

The slope for the injection spectrum for protons and electrons is assumed. The normalization is defined by the SNR rate.

Computed without further assumptions

The model reproduces the FIR emission with dust emissivity, and uses it + the CMB for computing losses. The magnetic field is defined by requiring that the synchrotron-free free emission of the steady population of electrons matches observations.

IR-FIR luminosity of Arp 220IR-FIR luminosity of Arp 220

Blackbody optical contribution

Non-thermal radio contribution

the FIR emission is modelled by dust, having an emissivity law proportional to

Radiation is coming from each of the components of Arp 220, assuming that it is radiated with a single temperature and emissivity law.

The model (sum of the threecontributions) derived to fit the data (= 1.5, T = 42.2 K)

• simple & conservative model• avoids model degeneracies by increasing the number of free parameters

Steady distribution of protons in each of the components of Arp 220.

Example for a steady distribution of electrons and positrons in a western-likestarburst (with B = 10 mG). The contribution to the total steady distribution of the primary and secondary electrons and positrons is separately shown. The horizontal rectangle shows the region of electron kinetic energies where the steady distribution of secondary electrons is larger than that of the primary electrons. It is in this region of energies where most of the synchrotron radio emission is generated.

Radio emission of the steady population of electronsRadio emission of the steady population of electrons

EAST

WEST

DISK

Infrared

With the magnetic field strength given in the Table and the relativistic steady state populations of previous Figures, only the molecular disk is in magnetic energy equipartition.

Lines are not fits to the data but predictions of the model for a particular choice of parameters.

Now we have the steady population of electrons and positrons and the IR dust emission Now we have the steady population of electrons and positrons and the IR dust emission that is in agreement with all observations & with that population we compute the that is in agreement with all observations & with that population we compute the

gamma-ray fluxgamma-ray flux

EGRET upper limits

The emissivity of high energy photons is the largest in the western extreme starburst, the most active region of star formation. The differential flux, shown in the right panel without considering absorption

effects, shows the influence of volume. The disk flux is the largest, and the nuclei are now subdominant. Nevertheless, only the western starburst provides more than one fourth of the total flux

Opacities to gamma-ray escape in the different components of Arp 220 as a function of energy.

At the highest energy, the opacity is dominated by processes, whereas Z dominates the opacity at low energies. Significant opacities are only encountered above 1 TeV.

The inset shows the total, and the contributions to the total opacity, in the case of the western nucleus of Arp 220 for this range of energy.

The equation of radiation transport is solved to compute the predicted fluxestaking into account all absorption processes.

Results for integrated gamma-ray fluxes are:

This would make Arp 220 observable for GLAST and VERITAS/HESS/MAGIC telescopes. The latter would need < 100

hours to detect it.

Be aware of cross sections for pion decays above 1 TeV.

Proof of concept beyond ARP 220 detectability itself:LIRGs well within the 100 Mpc sphere should be TeV sources!

SummarySummary

LIRGs and ULIRGs, following simple population analysis, are to be LIRGs and ULIRGs, following simple population analysis, are to be detected as gamma-ray sourcesdetected as gamma-ray sources Starburst activity – cosmic ray populations – difussionStarburst activity – cosmic ray populations – difussion

Detailed analysis for ULIRG Arp 220 confirms this. Many other Detailed analysis for ULIRG Arp 220 confirms this. Many other LIRGs (several tens) may appear in the forthcoming catalogsLIRGs (several tens) may appear in the forthcoming catalogs first multiwavelength analysis of Arp 220 (the strongest site of first multiwavelength analysis of Arp 220 (the strongest site of

star formation known, the nearest ULIRG)star formation known, the nearest ULIRG) first estimation of the magnetic field – compatible with Zeeman first estimation of the magnetic field – compatible with Zeeman

splitting measurements in Galactic active star forming sitessplitting measurements in Galactic active star forming sites observations with GLAST & Cherenkov telescopes are possibleobservations with GLAST & Cherenkov telescopes are possible

IC hard X-ray emission in the model were also computed and found in IC hard X-ray emission in the model were also computed and found in agreement with OSSE and RXTE upper limitsagreement with OSSE and RXTE upper limits

EBL do not affect photon propagation once gamma-rays leave the galaxy EBL do not affect photon propagation once gamma-rays leave the galaxy (very low redshift)(very low redshift)

Thank you.Thank you.

Scoville et al. 1997: Arcsec imaging of CO emission

Integrated intensity map for the brightest CO (2-1) components peaks at the positions of the near-infrared nuclei, indicated by the + symbols.

Losses for protons and electrons: exampleLosses for protons and electrons: example

D. F. Torres 2004

D. F. Torres 2004

Arp 220: Geometry

1.6 GHz OH emission. The grayscale is continuum and the boxes are line observations done with MERLIN (Rovilos et al. 2003)

1975-1982, 1975-1982, COS-BCOS-B, orbit resulted in a large and , orbit resulted in a large and variable background of charged particles, variable background of charged particles,

~200,000 ~200,000 γγ-rays.-rays.

Context: The evolution of the gamma-ray skyContext: The evolution of the gamma-ray sky

1991-2000, 1991-2000, EGRETEGRET, large effective area, good , large effective area, good PSF, long mission life, excellent background PSF, long mission life, excellent background

rejection, and >1.4 × 10rejection, and >1.4 × 1066 γγ-rays-rays

Unidentified sources: 120 at high latitudes, 80 at low (|b|<10) latitudes. 66 Possible gamma-

ray active galactic nuclei. --- 6 pulsars.

D. F. Torres 2004

Simulated LAT maps (>100 MeV, >1 GeV, 1 yr). More than 10000 point sources. Simulations by

Seth Digel

Future surveys (with GLAST)Future surveys (with GLAST)

D. F. Torres 2004

The multi-messenger context & the evolution of the sensitivityThe multi-messenger context & the evolution of the sensitivity

From S. Ritz

From Torres & Anchordoqui 2004

Complementary Capabilities

D. F. Torres 2004

Perhaps the main discovery in the EGRET era…Perhaps the main discovery in the EGRET era…Diversity of high-energy gamma-ray sources Diversity of high-energy gamma-ray sources

VariabilityVariability: the more direct way to acknowledge the : the more direct way to acknowledge the existence of several different gamma-ray sourcesexistence of several different gamma-ray sources *Clearly defined variable and non-variable sources

*No correlation with sky position

Possible Galactic Sources:-Pulsars, Plerions and SNRs (NV)-Isolated Black holes, X-ray binaries, microquasars (V)-Stars (?)

Possible Extragalactic Sources:-AGNs (V), Radiogalaxies (?)-Clusters of galaxies (NV)-Regions of star formation, starbursts and ULIGS (NV)

D. F. Torres 2004

Gamma-ray emission from the interstellar mediumGamma-ray emission from the interstellar medium

High-energy gamma-rays are produced in cosmic-ray interactions with interstellar gas and photons Cosmic-ray production is associated with regions of massive star

formation (e.g., SNRs, colliding OB stellar winds) This represents approximately 90% of the high-energy gamma-ray

luminosity of the Milky Way (~106 solar)

~60% of all EGRET gamma-rays were diffuse emission from the Milky Way

Diffuse emission from external galaxiesDiffuse emission from external galaxies

Only one other external galaxy detected in the light of its diffuse emission – LMCOnly one other external galaxy detected in the light of its diffuse emission – LMC The problem is distance: Milky Way at 1 Mpc would have a flux of about 2.5 x The problem is distance: Milky Way at 1 Mpc would have a flux of about 2.5 x

1010-8-8 cm cm-2-2 s s-1-1 (>100 MeV), well below EGRET’s detection limit (>100 MeV), well below EGRET’s detection limit

LMC

(1.9 ± 0.4) x 10-7 cm-2 s-1

EGRET IRAS

30 Doradus: extensive massive SFR and molecular clouds

The most interesting case?The most interesting case?G347.3-0.5G347.3-0.5

Positional coincidence of the non-variable EGRET gamma-ray source, 3EG J1714-3857, with a very massive (~3×105 solar masses) and dense (~500 nucleons cm-3) molecular cloud…

This molecular cloud is interacting with the X-ray and TeV gamma-ray emitting SNR G347.3-0.5…

The cloud region is near the shell of the SNR, and shines at GeV, but it is of low radio and X-ray brightness…

Butt et al. ApJ Letters, 562, 167 Butt et al., Nature 418, 499 Enomoto et al., Nature 416, 823 Reimer & Pohl, A&A 390, L43 Torres et al. Phys. Rept. 2003

Slane et al. ApJ 525, 357 (1999)

The clouds that seem to interact with it are pushed away as a cause of the blast wave shock

Total molecular column density over a wide section of the fourth Galactic quadrant around G347.3-0.5. The lowest contour is well above the instrumental noise (9) to emphasize the relatively low molecular column density toward the SNR.

Molecular environment of the SNR G347.3-0.5

Slane et al. ApJ, 1999

The distribution of 781 line intensity ratios, R={CO(J=21)/CO(J=10)}, measured every 15′ in the region from l=346.5348.5; b= -0.5+0.5, and averaged over 5km/sec bins of velocity between vlsr= -150 km/sec +50

km/sec.

The mean of the distribution, ~0.72, agrees with the average unexcited value in the Galactic plane. The cloud however, show values 3 above that.

More precise indication of interaction with molecular material

Top 0.5% of all values measured. All other bins with high R are well outside the 3EG field

The complete panorama for SNR G347.3-0.5

ROSAT X-ray contours. Emission from the bulk of the SNR rim can be seen with particular enhancements along the west/northwest regions, where bright non-thermal radio emission is also seen. The total radio flux is well below 10 Jy, Slane et al. ApJ 525, 357 (1999)

Red depicts the TeV significance contours. The flux was (5.3 ± 0.9 [statistical] ± 1.6 [systematic]) x 10-12 photons cm-2 s-1 (at E>1.8 ± 0.9 TeV). Muraishi et al. AA354, L57 (2000).

While electrons give rise to the bulk of the non-thermal radio, X-ray and TeV emission in the NW, the CR protons and ions are exposed at GeV energies via their hadronic interactions in the dense material of

cloud A, leading to pion gamma-decay GeV emission in the NE.

The expected -ray flux at Earth coming from the SNR is (Drury et al. 1994),

ESN is the energy of the SN in ergs, is the fraction of the total energy of the explosion converted into CR energy, and n and d are the number density and distance. In most cases, this flux is far too low to be detected by EGRET, but the existence of massive clouds in the neighborhood can enhance the emission

Here M is the mass of the cloud in thousands of solar masses, k is the CR enhancement out of the usual emissivity (~2.2 10-25 s-

1 H-atom-1).

0

23

910)100( kqDMMeVEF kpc

The gamma-ray luminosity

The single power-law fit (=-2.3) through all points (solid black line) is not at ease with the enhancement at 50-70 MeV.

This feature is consistent with the long-sought SNR neutral pion gamma-decay resonance centered at 67.5 MeV.

The red curve is an expected spectrum due to hadronic CR interactions.

As Schlickeiser has pointed out, the bremsstrahlung from secondary electrons due to the decay of hadronically produced charged pions, ± ’s, will contribute significantly at energies lower than ~70 MeV.

Schlickheiser 1982

The spectrum of the EGRET sourceThe gamma-ray spectrum

However: deviationfrom other points is lessthan 3ust yet be

Confirmed.

The electron flux needed to explain the GeV emission via e- bremsstrahlung in the cloud material should also produce an enhanced synchrotron radio emission. The expected ratio of GeV bremsstrahlung

flux to radio synchrotron flux is:

, s cm Jy )(

103.4

)

)MeV 100( 1-2-1-2/)1(H

2/)1(μGcm

21

Jy

3

p

zpBn

pcF(ν

EFR

),( )1( )102.3( 10 22/)1(15)1(5 papc(p) pp

Measured from CO obs.

Measured from TeV obs..

Frequency of observations

Spectral index

Observed by EGRET

This is what we want: radio fluxprediction if the flux is leptonic

GeV emission is not leptonic

Violates the observed upper limit by a factor of 20 at 843 MHz.

No other plausible candidate in the 3EG fieldNo other plausible candidate in the 3EG field There are two recently discovered pulsars within the

95% confidence location contours of 3EG J1714-3857: PSR J1715-3903 and PSR J1713-3844

Their spin down luminosity is such that they cannot contribute significantly to the observed gamma-ray emission.

Two other SNRs within the EGRET 95% contours: CTB37A&B. They can both be ruled out as strong gamma-ray emitters because of both: their large distance (11.3 kpc) and the low density medium around them

No WR or Of massive stars in the field, no X-ray binaries or black hole candidates

Torres, Butt, Camilo, ApJ Letters, 560, 155

In summary: strong hints that the blast wave shock of SNR

G347.3-0.5 is a site of hadronic cosmic ray acceleration

• TeV cosmic ray electrons are accelerated in this SNR; • the abutting cloud material is extremely excited; • the cloud region is of low radio and X-ray brightness; • the GeV flux is non-variable and in agreement with that

expected from o gamma-decays; • the spectral index is as expected for an hadronic CR

source population (but the desired confidence level not yet reached)

• there are no other candidate GeV sources within the 95% location contours of 3EGJ1714-3857

This is probably the best existing evidence for a connection between EGRET unidentified sources and supernova remnants. There are other very similar cases though: W66, W28, etc.

Recent claims:TeV detection of RXJ 1713.7-3946 by CANGAROO II:

Enomoto et al. 2002, Nature 416, 823

Source location:NW rim of the SNR (basically the same position found by Muraishi et al. 2000, coincident with X-ray maximum).

Against their own previous claims: CANGAROO favor a hadronic origin for the measured TeV emission.

Can the TeV emission be hadronic as well?

Power law with steep index -2.8.

Problems with Enomoto’s fitProblems with Enomoto’s fit

Reimer & Pohl, astro-ph/0205256; Butt, Torres, et al., Nature 418, 499 (2002)

•The source is not sub-GeV!

Furthermore: Matter density in the NW rim: less than

0.1 cm-3, not 100 cm-3, as CANGAROO assumed to plot their curve.

Finally, EGRET and TeV source are not even spatially coincident !

But, there isstill the possibilityfor a hadronic origin ifthe TeV photonsdetected are actually coming fromCloud B!

EGRET stackingsearches

Cillis, Torres, Reimer 2004. Submitted to ApJ

D. F. Torres 2004

High energy emission from supernova remnants and regions of star formation Diego F. Torres...

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